Potterton E28 Fault Code
The E28 fault is triggered when the Potterton boiler cannot detect water circulating through the primary circuit. The pump is not moving water, or the flow sensor cannot confirm movement. Common on Potterton boilers over 8 years old — pump wear follows the same timeline as Baxi equivalents due to shared BDR Thermea components.
What is the Potterton E28 fault code?
The Potterton E28 fault is triggered when the PCB detects insufficient water flow through the primary circuit during a heating cycle. The flow sensor monitors water movement after the pump starts. If circulation is not confirmed within the expected window, E28 locks out the boiler to prevent heat exchanger damage from running dry or without adequate flow. Because Potterton and Baxi share the BDR Thermea platform, the E28 code, flow sensor, and pump components are the same on both brands — and repair approaches are identical.
What causes the E28 fault?
The pump impeller seizes from corrosion. Particularly common in South London where hard water corrodes pump internals. The motor may still run but cannot move water.
Air trapped inside the pump prevents flow. The impeller spins but no water is circulated — resolved by bleeding the pump.
Heavy magnetite sludge accumulates over years without a magnetic filter, restricting flow below the sensor threshold.
The flow sensor can fail and show E28 even when the pump and circuit are functioning correctly. Less common than pump faults.
Limescale narrows the water path inside the heat exchanger — even a working pump cannot push adequate flow through a heavily scaled exchanger.
A stuck diverter valve prevents water from entering the heating circuit. Common on Potterton combi models after 8–10 years.
What you can safely check yourself
Low pressure reduces pump performance. Repressurise to 1.2 bar via the filling loop if below 1 bar, then attempt one reset.
After resetting, place your hand on the boiler casing near the pump. Silence where you'd expect vibration suggests a seized impeller.
Air in the system can cause flow sensor misreadings. Bleed each radiator from the top floor down, repressurise to 1.2 bar, then attempt one reset.
Do not reset the boiler more than once if the fault code returns immediately. Repeated resets without diagnosis can mask a worsening fault.
What needs a Gas Safe engineer
- Test pump speed and current draw with a multimeter
- Manually free a seized pump impeller if possible
- Bleed air from the pump if an airlock is suspected
- Test flow sensor output and replace if faulty
- Power flush if sludge is restricting primary circuit flow
- Check and free a stuck diverter valve on combi models
- Replace the pump if seized beyond recovery
Seized pumps are disproportionately common across South London — Wandsworth, Merton, Lewisham, Lambeth, Southwark, Greenwich, and Bromley — where hard water corrosion inside the pump casing and magnetite sludge accumulation combine to create ideal conditions for impeller seizure. Potterton boilers wear at the same rate as Baxi equivalents in these areas. Reion recommends fitting a magnetic filter at first service and completing an annual pump check on every Potterton in South London.
How much does a E28 repair cost?
Costs below are UK averages. Reion provides a fixed quote after the £80 diagnostic visit — no obligation to proceed.
How to reset a Potterton boiler showing E28
Check system pressure and repressurise to 1.2 bar if below 1 bar.
Bleed any cold radiators, then repressurise again.
Hold the reset button for 3 seconds.
Listen for pump operation within 10 seconds of reset.
If E28 returns, call a Gas Safe engineer.
Pump replacement costs £280–£420 all in on a Potterton boiler. Because Potterton shares pump components with Baxi through the BDR Thermea platform, parts are readily available. On a boiler under 12 years old, pump replacement is always worth doing rather than replacing the whole boiler.
Common questions about the Potterton E28 fault
What does a Potterton E28 fault code mean?
Is the Potterton E28 the same as a Baxi E28?
Can I fix a Potterton E28 fault myself?
Why is E28 common on older Potterton boilers in London?
How much does a Potterton E28 repair cost in London?
Other Potterton fault codes
Need a Potterton engineer in London?
Reion is Gas Safe registered (919881), based in South London, and available 24/7. Fixed price after the diagnostic visit — no hidden charges.
